The disclosed embodiments of the present invention relate to demodulating a received communication signal, and more particularly, to a narrow-band interference detector for performing a narrow-band interference detection according to a signal generated from an equalizer, a signal receiver employing a narrow-band interference detector and controlling demodulator parameter setting according to a narrow-band interference detection result, and related methods thereof.
When a customer gets his/her TV set, channel scan is usually the first action enabled by the customer to search the program channels available from the service provider. In general, the channel scan time is typically an important index of the channel acquisition performance of a demodulator included in a signal receiver of the TV set. Taking a TV set with a signal receiver devised for receiving a digital cable TV signal for example, a non-data aided (NDA) acquisition is required as there is no training signal provided from the service provider, and a decision-directed (DD) acquisition would take place of the NDA acquisition if the NDA acquisition converges and the output signal-to-noise ratio (SNR) is high enough. However, as the signal receiver may confront different reception conditions, a default demodulation configuration/parameter setting of the demodulator cannot cope with all of the possible reception conditions. For example, the reception of the digital cable TV signal may be affected by multipath interference, phase noise, burst noise, adjacent channel interference, co-channel interference, etc. In a conventional design, the receiver has a plurality of predefined candidate demodulation parameter settings stored therein, and employs a time-out mechanism to change the demodulation parameter setting utilized by the demodulator. More specifically, a system controller of the receiver selects one of the predefined candidate demodulation parameter settings to configure the demodulator, and if the demodulator configured by the selected demodulation parameter setting fails to successfully decode the received signal within a predefined elapsed time (i.e., a predefined time-out period), the system controller will select another predefined candidate demodulation parameter setting to configure the demodulator, and the demodulator configured by the new demodulation parameter setting will decode the received signal again. In other words, each time the time-out period is expired and the signal reception failure occurs, the system controller will configure the demodulator by a new demodulation parameter setting selected from the predefined candidate demodulation parameter settings. The time-out mechanism is operative to change the demodulation parameter setting of the demodulator until the signal reception is successful under the current reception condition.
As one can observe, the performance of the time-out mechanism depends on the length of the predefined time-out period (i.e., the allowable elapsed time for one signal reception session incorporated with a selected candidate demodulation parameter setting). In a case where the time-out period is too long, it may result in unpleasant channel change experience and unacceptable channel scan time. In another case where the time-out period is too short, the receiver may miss some achievable reception chances, leading to a reduced number of program channels that are identified by the channel scan operation.
In view of above, there is a need for an improved time-out mechanism which can dynamically adjust the time-out period for achieving optimized signal reception performance of a signal receiver (e.g., a digital cable TV receiver).